Metamath Proof Explorer

Theorem pm2.49

Description: Theorem *2.49 of WhiteheadRussell p. 107. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm2.49 
|- ( -. ( ph \/ ps ) -> ( -. ph \/ -. ps ) )

Proof

Step Hyp Ref Expression
1 pm2.46 
 |-  ( -. ( ph \/ ps ) -> -. ps )
2 1 olcd 
 |-  ( -. ( ph \/ ps ) -> ( -. ph \/ -. ps ) )